MOF-on-MOF-derived Co3O4@ZnO@Hemin peroxidase-like nanozyme for ultrasensitive detection of organophosphorus pesticides in vegetables and lake water.

To address threats of organophosphorus pesticides (OPs) residues to food safety and environmental health, this study developed a core-shell-shell nanozyme (Co3O4@ZnO@Hemin) for sensitive OPs detection in multiple real samples. The nanozyme integrates nanocatalyst electronic effects with biomimetic hydrophobic microenvironment functionality, fabricated by pyrolyzing a ZIF-67@ZIF-8 metal-organic framework (MOF)-on-MOF precursor, followed by Hemin loading. Remarkably, this nanozyme exhibits specific peroxidase-like activity, attributed to the mesoporous Co3O4@ZnO structure that promotes electron transfer and provides bimetallic mixed-valence active sites. Meanwhile, Hemin incorporation further increases oxygen vacancies through electronic regulation and enhances hydrophobicity, synergistically boosting catalytic performance. Therefore, this nanozyme sensor platform achieved ultrasensitive acetylcholinesterase (AChE) detection with a detection limit (LOD) of 0.07 mU mL⁻¹ and quantitative trichlorfon detection (1-5 ng·mL-1, LOD 0.10 ng·mL-1), successfully applied to detect trichlorfon in lettuce, cucumber, bok choy, and lake water, with 90.21-105.91% recoveries and RSDs below 4.62%. This study provides a bioinspired nanozyme strategy for sensing.